This article is chiefly about the Routing Information Protocol for Internet_Protocol and IPv6.

The Routing Information Protocol (RIP) is one of the most commonly used Interior Gateway Protocol (IGP) Routing network protocol on internal networks (and to a lesser extent, networks connected to the Internet), which helps Routers dynamically adapt to changes of network connections by communicating information about which networks each router can reach and how far away those networks are.

Although RIP is still actively used, it is generally considered to have been obsoleted by routing protocols such as OSPF and IS-IS, although EIGRP, a somewhat more capable protocol in the same basic family as RIP (destination-vector routing protocols), also sees some use.

=History=

The routing Algorithm used in RIP, the Bellman-Ford algorithm, was first deployed in a computer network in 1969, as the initial routing algorithm of the ARPANET.

The earliest version of the specific protocol that became RIP was the Gateway Information Protocol , part of Xerox Parc s PARC Universal Packet internetworking protocol suite. A later version, named the Routing Information Protocol , was part of Xerox Network Services.

A version of RIP which supported IP addresses was later included in the Berkeley Software Distribution (BSD) of the Unix operating system, as the routed server, and various other vendors would impliment their own versions of the routing server. Eventualy RFC 1058 was issued to unify the various implimentations under a single standard.

=Technical details=

RIP is a distance-vector routing protocol, which employs the hop count as a routing metric. The maximum number of hops allowed with RIP is 15. Each RIP router transmits full updates every 30 seconds by default, generating large amounts of network traffic in lower bandwidth networks. It runs above the network layer of the Internet protocol suite, using User datagram protocol port 520 to carry its data. A mechanism called split horizon with limited poison reverse is used to avoid routing loops. Routers of some brands also use a holddown mechanism known as heuristics, whose usefulness is arguable and is not a part of the standard protocol.

In many current networking environments RIP would not be the first choice for routing protocol as its convergence times and scalability are poor compared to OSPF or IS-IS, and the hop limit severely limits the size of network it can be used in. On the other hand, it is easier to configure.

= Versions =

There are three versions of RIP, RIPv1 , RIPv2 , and RIPng .

RIPv1, defined in RFC 1058, uses classful address routing. The routing updates do not carry subnet information, lacking support for VLSM. This limitation makes it impossible to have different-sized subnets inside of the same network class. In other words, all subnets in a network class must be the same size. There is also no support for router authentication, making RIPv1 slightly vulnerable to various attacks.

Due to the above deficiencies of RIPv1, RIPv2 was developed in 1994 and included the ability to carry subnet information, thus supporting Classless Inter-Domain Routing. However to maintain backwards compatibility the 15 hop count limit remained. Rudimentary plain text authentication was added to secure routing updates; later, MD5 authentication was defined in RFC 2082.

RIPv2 is specified in RFC 2453 or internet standard 56.

RIPng, defined in RFC 2080, is an extension of the original protocol to support IPv6.

== See also == *IPX *Request for Comments

=Further reading=